An agricultural harvesting machine such as a combine includes a head and a feeder housing which remove the crop material from the field, gather the crop material and transport the crop material to a separator. In the case of thinner stemmed crops such as soybeans, wheat, etc. which may be cut with a sickle bar carrying a plurality of knives, the head may also be known as a cutting platform. The separator removes the grain crop material from the non-grain crop material. The grain is cleaned and deposited in a grain tank. When the grain tank becomes full, an unloading auger which is positioned alongside the combine during harvesting is moved to the unloading position in which the auger extends approximately perpendicular to the longitudinal axis of the combine. The combine drives alongside a vehicle into which the grain is to be unloaded, such as a semi-trailer, and the unloading auger is actuated to discharge the grain into the vehicle.
A cutting platform may generally be of two types. One type typically has a sheet metal floor with a dual feed auger near the rear of the cutting platform for feeding the crop material longitudinally to the feeder housing. A cutting platform of this type with auger feed is relatively common.
Another type of cutting platform, also known as a draper platform, utilizes a flat, wide belt, referred to as a draper or draper belt to convey crop material. The arrangement and number of belts vary among platforms. One style of draper platform has two or more side belts that convey crop material longitudinally, to the center of the platform, where a center feed belt moves the crop material laterally into the feeder housing. Each belt is wrapped around a pair of rollers, one being a drive roller and the other being an idler roller. An example of this type draper arrangement is disclosed in U.S. Pat. No. 6,202,397, which is assigned to the assignee of the present invention.
An advantage of a draper platform is that larger amounts of crop material can be transported without plugging, etc. For example, with wide platforms approaching 40 feet or even larger, the amount of crop material transported to the feeder housing can be substantial. With an auger feed platform, the crop material may bind between the auger and the back wall of the platform. In contrast, with a draper platform, the crop material is carried on top of the belt with less chance for plugging.
Advanced draper platforms provide a flexible cutting platform that follows the undulations of the field to more effectively collect crop material. The more effective arrangement for a flexible cutterbar assembly is to have a series of pivotally connected float arms where the pivot point of the float arms is as close to the surface of the field as practical. This feature allows greatly reduced draft loads when the agricultural harvester is traversing a field. In addition, it more effectively collects crop material that is close to the ground. While providing superior harvesting, this arrangement provides additional loads on the draper belt that is used to carry the crop material to a center section for processing. This is because the pivot point of the float arm, which journals the rollers for the belt, is not in line with the longitudinal rotational axis of the drive and idler rollers. As a result, the flexing of the rollers during movement through a field causes diagonal stresses on the rollers, which can lead to misalignment. It has been proposed in an application entitled Flexible Draper Belt for an Agricultural Harvesting Machine, having the same filing date and a common ownership with the present invention, to incorporate drive rollers that are translatable in a fore and aft direction to alleviate diagonal stresses that are placed on draper belts. Such an arrangement provides effective short term accommodation of belt flexure that would increase loading. However, for extended running, the drive rollers are acted on by gravity to move to a forward position, causing a pressure to urge towards misalignment.
What is needed in the art, therefore, is a system of the above type that accommodates long term operation in the condition in which stress is placed on a belt used in an agricultural machine.